Department of Electrical and Electronics Engineering
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Item Highly Sensitive and Selective H2 Gas Sensor Based on Pd-Pt Decorated Nanostructured Silicon Carbide Thin Films for Extreme Environment Application(World Academy of Science, Engineering and Technology, 2007-01) Mourya, Satyendra KumarPresent work describes the fabrication and sensing characteristics of the Pd-Pt decorated nanostructured silicon carbide (SiC) thin films on anodized porous silicon (PSi) substrate by RF magnetron sputtering. The gas sensing performance of Pd-Pt/SiC/PSi sensing electrode towards H2 gas under low (10–400 ppm) detection limit and high operating temperature regime (25–600 °C) were studied in detail. The chemiresistive sensor exhibited high selectivity, good sensing response, fast response/recovery time with excellent stability towards H2 at high temperature. The selectivity measurement of the sensing electrode was done towards different oxidizing and reducing gases and proposed sensing mechanism discussed in detail. Therefore, the investigated Pd-Pt/SiC/PSi structure may be a highly sensitive and selective hydrogen gas sensing electrode for deployment in extreme environment applicationsItem Enhanced Optical Absorbance Of Hydrophobic Ti Thin Film: Role Of Surface Roughness(IJMS, 2016) Mourya, Satyendra KumarIn the present work, structural, morphological, optical and wettability properties of DC magnetron sputtered titanium (Ti) thin films have been investigated. The nanostructured Ti thin films were deposited on glass and silicon substrates at various deposition angles, θD = 0°, 30°, 45° and 60°. HCP structure of Ti thin films with preferred peak orientations (100) and (002) were revealed from XRD. It was observed that as the deposition angle increases, film thickness (~260 - 100 nm) as well as average crystallite size (~27 - 11 nm) of Ti thin films decrease. Significant changes in topography of the films, with change in deposition angle, have been observed. The optical and wettability results suggested that transmission, reflection, absorption and water contact angle of Ti thin films are strongly influenced by deposition angle due to change in its surface roughness. The large near infrared (NIR) absorbance (~ 66 - 75%) was found for the sample deposited at θD = 30°, which exhibited hydrophobic (~ 94.6°) nature with high surface roughness (~ 28 nm).Item Development of Pd-Pt functionalized high performance H2 gas sensor based on silicon carbide coated porous silicon for extreme environment applications(Elsevier, 2019-03) Mourya, Satyendra KumarPresent work demonstrates the hydrogen gas (H2) sensing characteristics of palladium-platinum (Pd-Pt) functionalized silicon carbide (SiC) thin film grown on porous silicon (PSi) substrate for high temperature applications. Nano-crystalline SiC thin film was deposited by RF magnetron sputtering on anodized PSi substrate. The loading of discrete ultra-thin Pd-Pt bimetallic catalytic layer was carefully controlled by varying the sputtering parameters. The proposed device architecture (Pd-Pt/SiC/PSi) revealed significant advantages, such as stable high sensing response, large tunable detection range (5–500 ppm), fast response/recovery time, excellent reproducibility, high selectivity, wide operating temperature regime (25–500 °C) and good durability. The observed high response may be ascribed to the combined effect of enhanced catalytic activity of bimetallic Pd-Pt layer and increased surface area of the proposed sensor.Item Effect of annealing parameters on optoelectronic properties of highly ordered ZnO thin films(Elsevier, 2019-09) Mourya, Satyendra KumarIn the present work, tuning in optoelectronic properties of sputter deposited zinc oxide (ZnO) thin films on ITO coated glass substrate have been investigated as a function of annealing parameters. Although, the annealing treatment is needed to tune the optoelectronic properties of ZnO layer but it can also modify the electrical properties {a drastic change in sheet resistance (13 Ω/sq. to 23 ohm/sq.) was observed at an annealing temperature of 200 °C} of underlying ITO substrate, which restricted maximum annealing temperature to 200 °C for ZnO at ITO. Vertically standing array of ZnO nano-pipes having single crystal orientation (002) with hexagonal structure, large crystallite size (∼24 nm), lowest lattice strain (0.621%), highest surface roughness (∼16 nm), and lowest Rsh (12.3 KΩ/sq.) were obtained for sample annealed at 200 °C for 60 min. The XPS study also revealed that the sample annealed at 200 °C for 60 min contains lowest oxygen related vacancy (23.7), which favors the facile electrons transport when ZnO is used as an electron transport layer (ETL). SE and UV–Vis results revealed best optical parameters i.e., highest transmittance (T∼ 89%), refractive index (n = 1.98 at 480 nm), and band gap (Eg = 3.30 eV), for the sample annealed at 200 °C for 60 min. These results indicated that ZnO nano-pipes based ETL may be a promising candidate for low temperature, high mobility, and cost-effective optoelectronic devices.Item Surface modification of sputter deposited γ-WO3 thin film for scaled electrochromic behaviour(Elsevier, 2019-10) Mourya, Satyendra KumarIn this research work, the synthesis and the electrochromic (EC) performance of the active material (γ-WO3) is reported. Nanoporous γ-WO3 thin film was grown directly on the indium tin oxide (ITO) coated glass substrate using DC magnetron sputtering in a reactive environment (Ar:O2 = 2:1) at room temperature (RT). To achieve the nanoporous-nanocrystalline behaviour of the active material, a thermal treatment (250 °C) was given, which modified the compact film surface into nanospheres. This surface modification is responsible to alter the physical, optical and electrochromic properties of the active material. The physical properties of the active material were probed in detail using X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and energy-dispersive X-ray analysis (EDX). The optical and electrochromic behaviour of the active electrode material was analyzed using UV–Vis spectroscopy and cyclic voltammetry (CV). It has been found that the modified electrode exhibited large optical modulation (46%), high reversible redox behaviour (higher current density) and good cyclic stability at least upto 500 cycles, causes scaled EC behaviour. This electrochemically active architecture allow one to fabricate the device for energy harvesting applications. Our work indorse human comfort with financial benefits and may play a crucial role in “green nanotechnology”Item The role of non-homogeneous barrier on the electrical performance of 15R–SiC Schottky diodes grown by in-situ RF sputtering(Elsevier, 2022-10) Mourya, Satyendra KumarIn the present work, we have demonstrated the impact of barrier inhomogeneities on the electrical characteristics of silicon carbide (SiC) based Schottky barrier diodes (SBDs). Ohmic and Schottky contacts were deposited on RF sputtered 15R–SiC film under optimized growth conditions. Forward biased current-voltage (I–V) measurement in the temperature range of 300–420 K was employed to extract the diode parameters (barrier height, ideality factor, and Richardson constant), considering the thermionic emission (TE) as dominant charge transport mechanism. The obtained value of barrier height φB and ideality factor n exhibited anomalies as compared to theoretically predicted values. It was attributed to the co-existence of multiple charge transport mechanism owing to defect induced lateral barrier inhomogeneities at the metal-semiconductor interface. Further, Gaussian distribution of φB, as established by Warner and Guttler was incorporated along with TE model to analyze the temperature dependent I–V data to understand the non-ideality in diode parameters. Eventually, the obtained diode parameters as per the modified charge transport mechanism were found to be in close alignment with the predicted values.Item Coexistence of Space Charge Limited and Variable Range Hopping Conduction Mechanism in Sputter-Deposited Au/SiC Metal–Semiconductor–Metal Device(IEEE, 2023-02) Mourya, Satyendra KumarDespite being the cornerstone of high-temperature and high-power applications, the fabrication of silicon carbide (SiC) thin films has been a major challenge among research activities related to wide bandgap semiconductors. As almost all the reported SiC thin films produced by RF sputtering are amorphous, the growth of crystalline thin film on p-type silicon substrate at high temperature (>900 °C) is presented in this work. A metal–semiconductor–metal (MSM) device is fabricated with gold (Au) electrodes by sputtering. A unique behavior of current–voltage ( I – V ) characteristics is found in different voltage regimes. The thermionic emission model fails to explain the observed I – V characteristics. To understand the current transport mechanism in detail, I – V characteristics are carried out in the temperature range 250–380 K and divided into two voltage regimes, below and above 1 V. Below 1 V, variable range hopping mechanism (VRH) is found to be dominant and above 1 V, and ohmic conduction followed by space charge limited conduction (SCLC) is held accountable for the current transport mechanism. The analysis of both mechanisms indicates the presence of disorder states and gives valuable information about trap centers. The C – V characteristics further suggest the presence of interface states and deep traps. The advantageous implementation of this information will help to design optoelectronic, magnetic, and efficient energy storage devices to extract the maximum performance.Item Plasma Oxidized W-WOx Sensor for Sub-ppm H2S Detection(MDPI, 2017-08) Benedict, SamathaIn this work we have fabricated W-WOx core-shell nanowire structure using plasma oxidation, a CMOS compatible process, for sensing H2S gas. For comparison, the sputtered stack structure of W-WOx with different thickness ratios of W to WOx is fabricated and characterized for H2S sensing. The sensor fabricated using plasma oxidation process is found to be significantly better in sensing performance compared to the sensing results obtained from sensor fabricated using sputtering. The response of plasma oxidized sensor is 90.4% for 1 ppm H2S with response and recovery time of 4 s and 46 s respectively. In contrast, the sensor fabricated with sputtered film shows a response of 30.6% at 1 ppm with response and recovery times of 19 s and 84 s respectively. This study clearly indicates that plasma oxidation is an efficient method for development of stable sensors.Item Effect of thickness on the properties of ZnO thin films prepared by reactive RF sputtering(Springer, 2018) Gupta, Navneet; Kandpal, Kavindra; Shekhar, ChandraThis work reports structural and electrical properties of ZnO thin film deposited by reactive RF sputtering at the room temperature, for thin film transistor (TFT) applications. To study the thickness dependent effect, ZnO thin film of thicknesses 100, 200 and 800 nm were deposited over p-type silicon substrate. Structural properties of thin films have been characterized using X-ray Diffraction (XRD) and Atomic Force Microscopy (AFM). XRD analysis of 100 and 200 nm thick films shows dominant cubic phase of ZnO along with small presence of ZnO2, while; XRD analysis of 800 nm thick film confirms strong c-axis growth of wurtzite (W) ZnO. The XRD result confirm the polycrystalline nature of the thin film and shows that crystallinity improves with the film thickness. The AFM results confirm high step coverage of deposited thin films. From the thermionic transport model across the grain boundary it was observed that with an increase in film thickness mobility of carriers increases. The sheet resistance of undoped 100 and 200 nm ZnO film is found to be approximately 7 × 1011 Ω/□; while, the sheet resistance of 800 nm thick ZnO film shows almost 10 time reduction to 6.025 × 1010 Ω/□, owing to its improved crystallinity.